Making very hard shadows softer?
Depending on what you want, there are a couple ways to approach this.

Increasing the Size (in Properties > Lamp) of the main lamp to produce softer shadows:



Or Angle value if you are using blender 2.8 :



Here's a gif showing the size animated from 0.1 to 1:



Adding a second lamp to to put more light into the shadowed area:





Disabling Shadow rays for an object allows light to pass through and illuminate surfaces behind it. If this works for you, then all well and good, but be aware that this isn't a physically accurate phenomenon and may look strange in some situations.